As a conventional endoscope, an endoscope is known that is configured to acquire an normal light image such as a white light image and a special light image such as a fluorescent image, and the normal light image and the special light image thus acquired are displayed in a superimposing manner (see PTL 1 and 2, for example). As methods of superimposing the normal light image and the special light image, PTL 1 discloses a method in which such a special light image is added to one from among three color component images, i.e., the R component image, the G component image, and the B component image, that form the normal light image; and PTL 2 discloses a method in which a region of interest having high gradation value is extracted from the special light image, and the special light image in the region of interest is added to the normal light image.